Regenerated silk fibroin (RSF) gels are known to have porous microstructures that can be tuned to obtain controllable mechanical properties. The high strength of the fibroin gel, its porosity and its biocompatibility make it a potentially interesting biomaterial for applications such as 3D porous scaffolds for tissue engineering.
The gelation time of RSF depends on pH and concentration of fibroin in solution. The potential importance of fibroin gels is in biomedical research where the desirable pH is 7.2-7.4 for cell growth. It is observed that RSF of concentrations in the range 1 to 10 g/L can take as much as 30 to 60 days at pH 7 for gelation whereas, RSF of higher protein concentration in the range of 10 to 100 g/L takes 10 to 20 days at pH 7 to turn into a gel (Refer FIG. 1). RSF gels prepared from solutions of higher protein concentration do not have adequate porosity for cell ingress and growth. Therefore, it is desirable to create microporous gels from RSF of lower protein concentration at pH 7. Prolonged exposure to higher temperature ranges result in precipitation of proteins and loss of microporous structure, which is not desirable for application envisaged for RSF> Considerably long time is required for gelation of such solutions during which fungal growth is observed in silk solution/gel if, aseptic environment is not maintained. Considering its potential application in tissue engineering, use of antifungal agent needs to be avoidable so that cell line is not subjected to toxic environment. There is therefore a need to decrease the gelation time of RSF at pH 7 and room temperature. A. Lele et al in a poster for the International Congress on Rheology, 3-8 Aug. 2008 and in Phys. Chem. Chem. Phys., 2010, 12, 3834-3844 have studied the mechanism of gelation of regenerated fibroin solution. They also studied the structure and characteristics of the silk hydrogels formed.
References may be made to article titled, “Silk Polymer Designs for Improved Expression and Processing” by Dr. David L. Kaplan, discloses control of silk gelation wherein gelation of silk fibroin depends upon silk fibroin concentration, temperature and pH on gel formation and protein structure which can be related to primary sequence-specific features in the molecular organization of the fibroin protein. Further, the said article also describes Silk-Inorganic Nanocomposites—Silica Systems wherein cloning, expression and function of silk-R5 fusions for formation of silica nanocomposites were studied.
References may be made to article titled, “Novel nanocomposites from spider silk-silica fusion (chimeric) proteins” by Wong et al., 2006, discloses novel biomimetic nanocomposites approach to synthesize silica composites using fusion (chimeric) proteins. Fusion proteins have found applications in a wide spectrum of areas such as the biomedical field [including immunology, cancer research, and drug delivery (17-20)] and materials science [self-assembled materials (e.g., gels), quantum dot bioconjugates, sensors, and inorganic materials synthesis (21-27)].
References may be made to article titled, “Composite Material Made of Regenerated Silk Fibroin and Silica Sol” by Cheng Cheng et al. published on 2008/10 discloses that regenerated silk fibroin solution and silica sol were mixed to produce the silk fibroin/silica composite materials. In order to probe if there is interaction between silk protein and silica, and further more, whether the interaction can improve the mechanical properties of composite materials, the structure and properties of the silk fibroin/silica composite material were studied by dynamic mechanical analysis (DMA) together with scanning electron microscopy (SEM) and Raman spectroscopy. The SEM results revealed the good compatibility between silk fibroin and silica in the composite. Nano-sized silica particles dispersed evenly in the continuous matrices of silk fibroin. Raman spectra of the composite materials indicated that the silk fibroin was dominated by beta sheet conformation. Comparing to the pure silk fibroin material, the composites showed better dynamic mechanical properties.
References may be made to patent application WO 200512606, wherein application claims aqueous silk fibroin solutions and process for making the same, method of producing a fiber, silk foam, film and silk hydrogels. On page 30 of said PCT application, the study of influence of ions, pH, temperature and PEO on gelation of silk fibroin solution is discussed.
The prior art survey reveals that there is no document that teaches the process of acceleration of gelation, thereby decreasing gelation time. Particularly no prior art document teaches the process of acceleration of gelation time of silk fibroin employing an accelerating agent.